1. Field of the Invention
The invention relates to a series of high performance polymeric materials derived from norbornene derivatives and particularly to functional norbornenes as initiators for radical polymerization and polymers thereof.
2. Description of the Related Art
Polycarbonate (PC) has commonly been used as macromolecular material for optical purposes. Considerations which may influence the use of the optical material include bireffingence and water adsorption. With the development of high-density compact disks, it has become more difficult for the conventional polymers to meet such requirements.
A commercial material ZEONEX has been developed by Nippon Zeon, a polynorbornene with lower birefringence and water adsorption and improved optical characteristics. Such material can be prepared by ring-opening metathesis polymerization of a norbornene monomer in the presence of a metathesis catalyst and hydrogenated to become a saturated polynorbornene.
With the development of high-density compact disks, a method for producing a new polymeric material with lower birefringence and high transmittance for low wavelength range (blue light) has been developed. Non-crtystallinity of the polynorbornene is such that transmittance with respect to light of wavelength about 400 nm may approach 90%, since no aromatic ring is present in the main chain. In addition, the absence of a hydrophilic functional group in the main chain allows a ratio of water adsorption below 0.01%. Under the same condition, the polynorbornene has water absorption ratio far lower than that of the polycarbonate (PC). Further, glass transition temperatures of the polynorbornene and polycarbonate (PC) fall within the same temperature range (about 123° C.).
Recent attention has been paid to hydrogenated products of polymers produced by ring-opening metathesis polymerization of norbornene-type monomers such as tetracyclododecene, dicyclopentadiene (DCP), and tricyclopentadiene, etc. These hydrogenated products can serve as optical material for use in an optical disk, optical lens, or transparent film, etc. (see JPO60-26024, JPO1-24826, JPO63-264626, EP303, 246, JPO-63-317520 and JPO-1-132656), since such hydrogenated products have excellent transparency and heat resistance and low susceptibility to moisture gain, with comparatively low briefringence and excellent moldability.
Olefin metathesis polymerization is a popular method in polymer synthesis. In recent years, the ring-opening metathesis polymerization of cycloolefin and the metathesis polymerization of non-cyclodiolefin have become very important in polymer synthesis. Along with development of new catalysts, the synthesis method of polymeric materials which contain various functional groups has further developed correspondingly.
While organometallic catalyst use in metathesis polymerization has been popular for some time, the organometallic catalysts are not suitable in metathesis polymerization of the monomer which contains various functional groups and is also sensitive to moisture and oxygen gas. For example, tungsten (W), titanium (Ti), molybdenum (Mo) and ruthenium (Ru) catalysts are the most popular catalysts used in the ring-opening metathesis polymerization of cycloolefin, wherein ruthenium (Ru) catalyst is the most tolerant catalyst with respect to water and oxygen gas in the metathesis polymerization. The metathesis polymerization can be carried out in an aqueous solution in the presence of ruthenium (Ru) catalyst. For example, the catalyst of {Cl2Ru(CHPh)[P(C6H11)3]2} developed by Grubbs et al. in 1996 is suitable for ring-opening metathesis polymerization of cycloolefin. More particularly, the polymerization of the monomers with functional groups can be carried out in the presence of such a catalyst because it is stable in air. In addition, such metathesis polymerization provides a high polymerization rate and large molecular weight of resulting polymer. Generally speaking, such reaction has accompanied with living polymerization.
The ring-opening metathesis polymerization of a norbornene-type monomer is carried out, in general, in the presence of a catalyst system consisting of an organometallic compound such as an organoaluminum compound and a tungsten and/or molybdenum-based metathesis catalyst (please refer to JPO46-14910), or a catalyst system containing an organometallic compound such as an organoaluminium compound and a transition-metal compound such as titanium tetrahalide (please refer to JPO41-20111 and JPO50-12199).
However, with use of the first catalyst system, the resultant polymer has a broad distribution of molecular weight and thus high birefringence, despite being obtainable in such high yields, that the residual monomer is minimally present in the reaction system when the reaction is complete.
With use of the second system, the molecular weight distribution of resulting polymer can be easily controlled. However, as the concentration of monomer in the reaction system decreases, the rate of polymerization also decreases accordingly. Hence, polymers by the ring-opening metathesis polymerization (ROMP) of the present catalyst system cannot be obtained in high yields. Moreover, a large amount of unreacted monomer remains in the reaction system when the polymerization has completed. It is very difficult to remove this unreacted monomer during purification of the polymer.
Hence, extensive research has been directed at ring-opening metathesis polymerization (ROMP) of cycloolefin derivatives to improve the reactivity of catalysts, focused on the development of side-chain-type liquid crystal, a triblock copolymer synthesized by two-step method, a polymer with various functional groups and a polymer having cross-linkable functional groups remained in the side chain thereof, etc. The introduction of the functional groups improves the optical characteristics and biochemical activity of the polymer. In addition, the cross-linkable functional groups such as methacryloyl in the side-chain can be introduced and applied as UV curing agent, coating material and photoresist.
Polynorbornene and its derivatives, the first commercial products genereated by ring-opening metathesis polymerization (ROMP), are an important engineering material. The materials are used with shape-memory polymers, shining apparatus, machine, electrical elements, tube, food packages and the like because of good transmittance, wide usable temperature range, good mechanical properties, and excellent moldability. In addition, the derivatives of polynorbornene such as acidic and aromatic polymers can serve as a photoresist for use in semiconductor manufacturing.
Although the polynorbornene and its derivatives have good transmittance, wider usable temperature range, good mechanical properties and excellent moldability, synthesis of new norbornene-type monomers and polymers are not well developed and problems associated therewith not easily overcome. Hence, the development of new norbornene-type monomers and their derivatives has great potential in various applications.